Low-temperature rotation!

Thanks to a new liquid nitrogen heat exchanger, the NMR division is now able to carry out NMR experiments on rotating solids at very low temperatures (samples at -80°C with a rotation speed of 20 kHz, or at -110°C with a rotation speed of 10 kHz). These temperatures were measured with a 3.2 mm probe at 18.8 T (800 MHz for the proton frequency). This exchanger is a highly advantageous replacement for the evaporator previously used for the experiments, as:

• maximum cooling capacity of -173°C at the exchanger outlet, compared with -70°C for the refrigeration unit previously used in rotation,
• cooling power is adjustable, reducing liquid nitrogen consumption to a minimum,
• liquid nitrogen can be topped up during experiments. This means that acquisitions can be made over several days, with fine control for greater safety of the equipment (probe, magnet).